With the invention and broad adoption of cellular telephone technology over the last two decades, thousands of artificial metal cellular transmission towers have been constructed and placed across the North American continent and indeed, throughout the world. These structures may be owned and operated by the major telephone carriers, tower companies and/or smaller private tower owners. A typical cell tower is designed to support multiple cellular antennas and transmission equipment in an elevated position above the surrounding terrain. A cell tower typically includes an upright support, for example a monopole, and a horizontal antenna mounting structure known in the industry as a “crow's nest.” This structure is located at or near the top of the upright support and typically provides a working platform for tower personnel. There is often a railing system placed around the crow's nest for both worker safety and for attaching additional equipment, such as additional antennas and the like. The crow's nest frequently includes a floor or platform portion to facilitate inspection, maintenance, and upgrade of the installed equipment. The platform portion may include a handrail assembly for worker safety. The height of cell towers varies greatly, but typically they extend well above the top of existing structures in a given area.
Examples of cell tower and crow's nest structures can be found, for example, in U.S. Pat. No. 5,954,305, to Calabro, U.S. Pat. No. 5,649,402, to Moore, and U.S. Pat. No. 6,563,475. Each of these patents is hereby incorporated by reference in its entirety.
The Osprey (Pandion haliaetus) is a majestic raptor and one of the most widely distributed birds in the world. It can be found in both temperate and tropical regions on all continents except Antarctica. In North America, the Osprey is a relatively common raptor species, breeding in at least 34 states of the USA and in most provinces in Canada. It is particularly abundant along the Pacific and Atlantic coastlines.
Migrant Ospreys generally arrive in the north during spring. They will breed during the boreal summer months and then return south to Central and South America in the fall. They feed primarily on fish and are most often found nesting near large bodies of fresh or salt water.
Ospreys select tall, isolated and broken-off tree snags, often selecting Douglas Fir, Spruce or Ponderosa Pine for nesting. They build large nests, typically composed of a heap of sticks. This material is selected and transported to the nest primarily by the adult male and then carefully situated atop the snag by the adult female. She will place a wide assortment of other materials (grasses, sea-weed, even twine) directly on the rough upper end of the snag.
Among raptor biologists, this species is known to exhibit a very strong nest philopatry, i.e., having a tenacious attachment to the same nest tree, year after year. Once a breeding pair is established at a particular nesting location, they can be quite difficult to dissuade from nesting at the same location in the future.
With the now vast profusion of manmade towers, and especially cell towers, built in North America over the last two decades, the telecommunication industry has inadvertently created a profusion of attractive nesting sites for Ospreys. For example, from the perspective of an Osprey, cell towers mimic large, isolated nesting snags. Such manmade towers therefore “encourage” Ospreys to extend their breeding range into new areas containing these towers. This includes geographic locations where they have not previously nested, including highly populated urban areas, often situated miles from water. Based on the present inventor's experience, Ospreys are rapidly adopting manmade towers as nesting sites in ever increasing numbers. As a result of the unprecedented range expansion, they are creating many new and unexpected difficulties for the cellular telephone industry. A particularly troubling aspect of this phenomenon is the probability that those young Ospreys hatched and raised on cell towers will automatically imprint on them and, upon reaching adulthood, adopt the same type of structures for raising their families. We can therefore expect more and more manmade towers to become occupied by a geometrically increasing Osprey population over time.
Under various international, federal and/or local laws, tower operators may have very limited options for responding when a raptor nests on a tower. For example, under the Federal Migratory Bird Treaty Act (MBTA), it is typically unlawful to take or disturb an active nest of a listed species (including Osprey) during the breeding season. This law is enforced by both State and Federal Wildlife authorities. Violators of the MBTA may be fined or even imprisoned for deliberate infractions of this law. As a result of this legislation, tower maintenance crews are legally prohibited from disturbing an active Osprey nest during the entirety of its breeding season, a period which may extend from February through September, an interval of seven months. Tower workers can be legally prevented from maintaining, repairing, or otherwise resolving any operational problems that may occur during this extended time period.
In addition, many raptors can cause both disruption and damage to operating towers. Ospreys are large birds weighing up to 4 pounds and having a wingspan of over 4 feet. During the breeding season, they carry literally hundreds of large sticks and other materials to the tops of towers.
During the nest construction process, Ospreys often drop foreign objects from a tower nesting site. This material may potentially strike workers below, or damage sensitive equipment located on or around the tower (e.g., transformers). Damage may be caused by direct impact, or direct electrical shorting of lines and/or insulators, or the like. Equipment at the top of the tower may also be damaged from impact or electrical shorting. There are many records of fires being started at Ospreys nests on electrical transmission towers caused by such shorts.
In terms of hygiene, Osprey nests are inherently “messy” places. Over the course of a normal breeding season, a family of Ospreys (two adults and up to four young) create hygiene problems and other hazards for tower workers. For example, an Osprey nest may typically include an extensive amount of bird feces on, in, around, and below the nest. There will be whole and partially eaten prey items, including dead fish, and other prey. We have also found many dangerously sharp objects littering active nests, including barbed wire, dried fish bones, and rusted nails.
Additional hazards to workers include the restriction of free and open access to the worksite atop the tower. Working at height is considered dangerous enough, but when physical movements are also limited and impeded by the presence of a large, often unstable mass of precariously balanced sticks, there is increased danger to the tower workers, both on and below the nest. Since Ospreys are known to add sticks to the nest each year, this danger will increase each summer as the nest increases in size, often substantially. The larger the nest becomes, the greater amount of mass is applied to a structure that may not have been designed to accommodate the additional weight, and associated stresses. This becomes particularly relevant in areas of North America that experience hurricanes.
In addition to their own equipment, cell tower owners often rent space on their structures to several different clients, generating income from their investment. Interruption of services caused by nesting Ospreys, particularly on an annual basis, may cause the tenant to move to a different, more reliable tower site, causing a significant loss of revenue to the tower owner.
More recently, bird strikes have become a major issue in aviation safety. For example, a well-publicized bird strike incident on 15 Jan. 2009, involving US Airways flight 1549 forced Captain Sullenberger to ditch an Airbus A320 aircraft in the Hudson River with 155 crew and passengers on board. The Federal Aviation Administration (FAA Advisory Circular 150/33B) has determined that Ospreys are a species of major concern for bird strikes. As such, Ospreys breeding near major airports present an especially dangerous hazard to aviation safety. For example, in June 2010, at Seattle-Tacoma International Airport in Washington State, an adult Osprey was struck by a jet aircraft on the runway. That strike was the major impetus for the creation of the invention disclosed herein.
As a career raptor biologist, the present inventor has worked with birds of prey since 1965 in a variety of capacities, including nest surveys, migration studies, wintering investigations, and raptor banding. From 2001 through 2012, he developed and coordinated the Raptor Strike Avoidance Program at Sea-Tac Airport, working in association with the Port of Seattle. During this period they have captured, tagged, and safely re-located nearly 400 birds of prey to locations away from the runway.
In 2004, a pair of Ospreys first moved into the vicinity of the airport. They adopted an inactive cell tower located southeast of the main runways. This was the first known Osprey nesting attempt in the vicinity of the airport. Although the birds attempted to construct a nest, they were not successful. In 2005, the pair returned to the same tower, completed a nest, and raised two young. Since Osprey, particularly recently fledged young, are known to be a major threat to aviation safety, a plan was implemented to remove the young Osprey from this nest at three weeks of age and re-locate them to a more suitable active nest, 40 miles north in Snohomish County, Washington, and well away from any active airport. This technique is known as “fostering” and was successful, the young being raised by their “foster” parents. However, the following year, the same adult Ospreys returned to the nest and bred. In 2009, a second pair of Ospreys adopted a cell tower located near the airport and began constructing another nest, although they were not successful in producing young. This event raised safety concerns among our group. We began to realize that nesting Ospreys were going to be an increasing problem in our area and that cell towers were obviously going to be their “road of ingress.” More Ospreys equated to increased aviation hazards. In 2010, this second pair returned and started to build and repair their nest once again. However, in June an adult Osprey (presumed to be one of these new adults) was struck by an aircraft on a runway not far from the nest. The bird was found alive but had lost a wing as a result of the strike.
This specific incident confirmed our fears and focused the present inventor's attention on the safety issues involving Ospreys nesting in the vicinity of major airports. The present inventor recognized that the solution to the problem would be to provide an effective deterrent to Ospreys nesting on local cell towers. If we could prevent them from nesting nearby, then there would be far lower risk of aircraft strikes. The challenge was to provide an effective deterrent to Osprey nesting on cell towers that would not significantly interfere with the normal maintenance and operation of the cell tower. It is essential for tower workers to have a relatively unimpeded work area in the potentially dangerous and hazardous situation like a cell tower platform high above the ground.
Because of these important emerging issues, the need for deterring Ospreys from adopting a cell tower prior to nesting becomes readily apparent. There is a need for a practical working device that will deter Osprey from building nests on cellular and other manmade towers.